ST. LOUIS (KMOX) – Just how common is an allergic reaction to antibiotics, such as the one that forced Miley Cyrus to cancel her concert at Scottrade Center Wednesday night?

Dr. Nirav Patel, an infectious diseases specialist at St. Louis University Hospital, says that just like any other medication, antibiotics can cause both side effects as well as true allergic reactions.

“If it is a true allergy, it can be life threatening,” he says. “But currently, most antibiotics are mainly just the antibiotic itself with minimal impurities, and while they can cause allergic reactions, they are fairly rare.”

Patel says a true allergic reaction to antibiotics is usually treated with adrenaline and an inhaler or an antihistamine like Benadryl and observation.

Thursday morning, Cyrus announced to fans via Twitter that she would not be released from the hospital in time to make her St. Louis show. She had canceled the previous night’s concert at Sprint Center in Kansas City as well.

the hospital is sayin i wont b released today😿 therefore Im not going 2 make it 2 St Louis. Im so sorry but somethings are outta my control.